High molecular weight nitro-substituted polyurethanes



. 3,087,961 HIGH MOLECULAR WEIGHT NITRO-SUBSTI- TUTED POLYURETHANES James R. Fischer, Claremont, Calif., assignorto Aerojetgleneral Corporation, Azusa, Califi, a corporation of No Drawing. Filed Feb. 7, 1961, Ser. No. 87,710 42 Claims. (Cl. 260-482) This invention relates to high molecular weight polyurethane polymers containing nitro groups.

The principal object of this inventionis to prepare high energy high molecular weight compounds useful as solid smokeless propellants.

The nitro-substituted polyurethanes of my invention are high energy solid propellants and can be used as a primary propulsion source in rocket propelled vehicles and can also be used as a propellant for artillery missiles. When used as the primary propulsion source for rocket vehicles, th'ey'can be convenientlyignited by a conventional igniter such as, for example, the igniter disclosed in assignees copending United States patent application Serial No. 306,030, filed August '23, 1952, now Patent No. 3,000,312. The propellant is preferably castin place in tubular form and restricted in the conventional manner with a relatively inert resin such as a .nonnitrated polyurethane foam or a'polyester resin inside a chamber having one end open and leading into a coventional venturi rocket nozzle. Upon ignition, large quantities of gases are produced and exhausted through the vnozzle, creating propulsive force.

The polyurethanes of my invention possess numerous advantages over the composite and double-base solid propellants commonly in use today. In the propellant substances of my invention, the oxidizer is an integrated part of the chemical compound, thereby enhancing the reproducibility of ballistic properties and eliminating dangerous and costly grinding-and mixing operations. In propellant compositions commonly in use at present, the oxidizing element is usually a finely divided inorganic oxidizing salt which is dispersed in some type of -combustible organic binder, usually an organic resin. Numerous problems are involved in the preparation of this type of propellant; namely, obtaining uniform dispersion of the oxidizing agent throughout the binding composition and at the same time preventing the formation of cracks and faults in the propellant grain itself.

Although it is desirable to avoid the need for incorpo rating additional oxidizer, the novel resins of my invention lend themselves to such use. Any solid inorganic oxidizing salt such as ammonium perchlorate, ammonium nitrate, or the like, can be used for this purpose in the conventional manner, for example, by the method disclosed in assignees U.S.' patent application Serial No. 829,180, filed July 20, 1959, by merely substituting the high energy resins of this invention for thefuel binder materials disclosed therein.

The polyurethanes of my invention, having no metals whatsoever present, are smokeless and, since all'the elements of'the propellant are integrated in the molecular chain itself, there are no difilculties encountered in dispersing the oxidizing component nor is it necessary to perform any difiicult and dangerous grinding and mixing operations.

The high specific impulse and high density of the polyurethane compositions of my invention render them eX- tremely valuable wherever weight and size considerations of the propellant charge are important.

In addition to these valuable propellant properties, it"

has also been found that these materials possess high temperature and impact stability, thereby rendering their production both safe and economical. V

The polyurethanes of our invention are conveniently United States Patent "Oce 3,087,961 Patented Apr. 30, 1963 2 prepared simply by reacting-a diisocyanate with a diol in accordance with the general reaction scheme set forth below:

0 H H 0 [i J'l IRl l-( l-OR -O- wherein R is a lower alkylene, nitroalkylene, 'nitraz'aalkylene, or nitrazanitroalkylene radical; R is a dialkoxynitroalkylene radical ora dialkyloxamide radical; and y is the number of repeating units in the polymer chain.

It will be appreciated that in any given batch of propellant individual molecules may vary in length from several to tens of thousands of repeating units, hence molecular weight figures represent statistical averages. The exact nature of terminal groupings is not known and will vary depending upon whether plasticizers, polymerizatiodagehts, etc, are present. Moreover, a given moleculef'may even form a ring and thus leave no dangling radicals. g

It has been found that the reaction time niay be shortened and higher molecular weight polymers obtained, for example, urethanes having molecular weights of the order "of about 75,000, by conducting the reaction in solutionin'the presence of a suitable catalyst. Any of the conventional catalysts used in the preparation of polyurethane resins can be used; however, several catalyst have been found particularly useful, among which are boron trichloride; boron trifluoride complexes, such as boron trifluoride etherate; and metal chelates, such as ferric acetylacetonate. Suitable solvents are dioxane, dimethylformamide (frequently abbreviated as DMF'), butyrolactone, acetone, etc. Where catalysts are employed, they can be used in quantities within the range from mere traces up to amounts equivalent to about 1 percent by weight of the total mass or even higher. The use ofcatalysts is not critical; however, for economic reasons it is usually preferable to use them.

The polyurethanes formed in the process of this invention can comprise either linear polymers or cross-linked polymers. The linear polymers are those formed from appropriate-isocyanates and alcohols without the addition of any cross-linking agent. That is, they are merely linear chains composed of alternate isocyanate and alcohol monomers.

The cross-linked polymers, on the other hand, are prepared by employing a cross-linking agent polymers, thus bonding these polymers together.

in addition to the isocyanate and alcohol monomers which acts as a bridge between the linear isocyanaite-alcohol y suitable cross-linking agent such as polyisocyanates, triols, glycerol, trimethylol propane, :tris-(hydroxymethyl) nitromethane, etc:, can be used without departing from the scope of my invention.

Plasticizers can also be incorporated into the polyurethanes of this invention if desired. Any suitable plasticizer familiar to those skilled the ant such as 4-nitrazapentanonitrile, 2,2 dinitropropyl-4-nitrazapentanoate, as well as those'c'omme'rcially available as such, can be employed. V v

The polyurethane polymerization reaction can "be effectivelycarri ed out'at any temperature; the only effect of temperature variation being a corresponding change in the rate of reaction. The polymerization can be con ducted at room temperature although higher temperatures increase the rate ofreaction and might be desirable in certain cases; however, the polymerization will also take place at temperatures much below room temperature and thus temperaure is not a critical variable.

It is evident from the reaction scheme set forth above that a wide variety of polyurethanes can be prepared by the method of this invention simply by varying the particular alcohol and isocyanate used in the reaction. EX- amples of diols useful in the practice of this invention are dialkoxynitrazaalkylene diols having the general formula wherein A and A are the same or different and are lower alkylene radicals and x is a whole number from 1 to 6, inclusive, and dihydroxyalkyloxamides having the general formula it i HOANHOC-NHAOH wherein A" and A are the same or different and are lower alkylene radicals. Specific examples of such diols are:

N,N'-bis (Z-hydroxyethyl) oxamide;

N,N'-bis 3-hydroxypropyl oxarnide; N,N-bis(Z-hydroxymethyl) oxamide;

N,N-bis 6-hydroxyhexyl) oxamide; N,N-bis(Z-hydroxypropyl) oxamide;

N( 2-hydroxyethyl) N 3-hydroxypropyl) oxamide; 5-nitro-5-aza-3 ,7-oxyl ,9-nonanediol; 5,7-dinitro-5,7-diaza-3,9-oxy-1,1 l undecanediol; 5,7,9-trinitro-5,7,9-triaza-3,1 1-oxy-1,13qtrideoanediol;

(H) 1302 1 Igor L Lilo. 1.1%. L J.

Lao. in. i L l I These compounds are prepared according to the general reaction wherein A, A, A, and A'" are the same or diiferent alkylene radicals, x is a small whole number from 0 to 6 inclusive, y is a small whole number from O to 2 inclusive, and X is a whole number greater than one.

Still another species of polyurethane included in my invention are polyurethanes containing the structural unit 5,7 ,9,1 l-tetranitro-S ,7,9;l 1-tetra-aza-3, 13-oxy-"1, IS-penrtadecanediol;

These polyurethanes are prepared according to the general reaction scheme:

5,7,9,11,13-pentanitro-S,7,9,11,13-pentaza-3,12-oxy-1,17-

heptadecanediol; 6-nitro-6-aza-4,8-oxy-1,l l-undecanediol;

6,8-dim'tro-6,8 -diaza-4, 10-dioxy l,l3-tridecanediol;

6-nitro-6-aza-3-9-dioxy-1,1 l-undecanediol; 6,8-dinitro-6,8-diaza-3 ,1 1-dioxy1,13-tridecanediol;

' 7-nitro-7-aza-4,10dioxy-1,13-tridecanediol;

9-nitro-9-aza-7, 1 l-dioxy-l ,17-heptadecanediol; 5,9-dinitro-5,9-diaza-3,1 l-dioxy-l, 1 3-.tr-idecanediol; 6,12-dinitro-6,12-diaza-3,15-dioxy-1,17-heptadecanediol;

and

' 5,7 ,9,1 1,13-pentanitro-5,7,9,1 1,13-pentaza-3,16-dioxy-1,

18-octadecanediol. Examples of isocyanates useful in the practice of this invention are: Lower alkylene diisocyanates such as- Methylene diisocyanate, Ethylene diisocy-anate, and 1,3-propane diisocyanate;

Nitroalkylene diisocyanates such as 3,3-dinitro-1,5-pentane diisocyanate,

Ll'w. l. to. J.

wherein A, A and A" are the same or different alkylene radicals, x is a small whole number from 0 to 2 inclusive, and X is a whole number greater than one.

To more clearly illustrate my invention the following examples are presented. It should be understood that these examples serve merely as a means of illustrating the invention and should not be construed as limiting the invention to the particular embodiments and conditions set forth therein.

EXAMPLE 1 Equivalent amounts of the monomers 3,3-dinitropentane-1,5-diisocyanate and 5,7,9,1l-tetranitro-5,7,9,11- tetra-aza-3,l3-oXy-1,IS-pentadecanediol (28 gm. total weight) were mixed with 70 ml. dry dioxan in a 500 ml. resin pot equipped with a stirrer. The reaction mixture was maintained at 50 C. for two weeks, then worked up by pouring it into ice water in a Waring blender. The white, granular polymer was filtered, washed with distilled water, then vacuum steam-distilled using 3.5 kg. steam at 25-30 C. After drying, the product weighed 26 gm. (93 percent theoretical).

Found Percent C, 28.34; Percent H, 4.51;

Percent N, 24.66. Relativeviscosity2 1:13, 2%il'112166t0116l21t 25 C. X-ray Polycrystalline.

Soluble in acetone, dioxan, tetrahydrofuran, and dimethylformamide.

EXAMPLE II Equivalent amounts of-the' monomers- "3,3-dinitropentane-1,5-diisocyanate and 5,7,9-trinitro-5,7,9-triaza-3,11- oxy-1,l3-tridecanediol (29.6 gm. total weight) were mixed with 50 ml. dry dioxan-"in a 500 ml. resin pot equipped with a stirrer. The-resin pot awas-heatedtiman oil-bath at a constant temperature of 50 C. The mixture was stirred eight hours in each' 24-hour period and gradually became more viscous. After 336 hours, 50 ml. dioxan was added. The solution was filtered to emove any foreign particles, .then poured into 500' mLflicefwater in the Waring Blendor. The whiteygrjanular polymer was washed twice with 500 of "distilled waterandtrlansferred to a 3-liter flask for vacuum steam distillation. A total of 3 kg.. of steam at 2530 .C. pot tempflnature. The polymer was filtered, vacpum dried over calcium chloride, .then over phosphoruspentdxide for 72 P:

hours. The yield of dry polymer was 26.0 gm.

Physical Properties Calc. specific ,impulseinr 179 lb. I. 9 sea/l b. -m.

X-ray Amorphous. Soluble acetone, dioxan, tetrahydrofunan, di-- methyl formarnide.

EXAMPLE n1 7 A mixture of 31 gm. 3,3-dinitroa1,5-pentane diisocy-. anate, 22 gm. N,N-bis(2-hydroxyethyl)ox amide,' and 250 ml. anhydrous dioxan was maintained at 85 CI for-192 During this time a viscous polymeric phase sephours.

arated. It was dissolved in dimethylformamide and the polymer was precipitated by pouring into water using rapid agitation. Thedried" product weighed 49 Physical Properties Cale. specific impulse 94 lb. ff sec/lb. m.-

Softening'l-range 80-100 0. Impact stability .....t .1*cm. /2 'kg. Relative viscosity..- 1.32, 1% in DMF at 9 C.

Calc. for C H N O Percent C, 37.14; percent H,

4.80; percent N, 20.00.

Found Percent C, 37.37; percent H, 4.76;percent'N, 19.89. 7 X-ray Amorphous. Soluble in dimethylformamide.

The diisocyanate compounds used as starting materials in the practice of my invention are conveniently prepared by reacting their corresponding dioyl chlorides with sodium azide and subsequently'heating to effect rearrangement to the desired diisocyanate. This procedure is de scribed in detail in assignees copendingUS. patent application Serial No. 198,493, filed November 30, 1950. The alcohols may be obtained by reacting the corresponding polynitramine alkylene dinitrates with an alkylene glycol. For example, 5,7,9 trinitro 5,7,9 triaza-3, =11-oxy-1,13-tridecanediol is conveniently prepared by reacting ethylene glycol and 2,4,6-trinitro-2,4,6-triazaheptane-1,7-dinitrate.

This application is a continuation-in-part ofcopending US. patent application Serial Nos. 453,155 and 453,156, filed August '30, 1954, both now abandoned.

I claim:

1. As new compositions of matter, the nitro-substituted-polyurethane polymers prepared by the method which comprises condensing a diisocyanate composition selected from the group consisting of lower alkylene diisocyanates, nitroalkylene diisocyanates, nitraza-alkylene diisocyanates, nitrazanitroalkylene diisocyanates, and mixtures thereof with a diol composition selected from the group consisting of dialkoxynitrazaalkylenediols, di-

'hydi-oxyalkyl oxamides, and mixtures thereof.

2.- A'compo'sition according to claim lwherein said condensing is carried out in the presence of a condensation catalyst.

3. A' composition according to claim 2 wherein said condensation catalyst is a composition selected from the group consisting of borontrifluoride, borontrifiuoride complexes, and metal chelates.

4. A composition according to claim 2 wherein said condensation-catalyst is ferric acetylacetonate.

5. As new compositions of matter, the'polyurethane polymers prepared "by the method which comprises condensing a dihydroxyalkyl oxamide with a lower alkylene diisocyanate.

6. As new compositions of matter, the nitro-substituted polyurethane polymers prepared by the method which comprises condensing a- -dihydroxyalkyl oxamide with a nitroalkylene diisocyanate.

7.As new"'compositions' of matter, the'nitro substituted polyurethane polymers prepared by the method which comprises condensing a dihydroxyalkyl oxamide with a nitrazaalkylene diisocyanate.

8. As 'newcompositions of matter, .the nitro substi tuted polyurethane polymers prepared by the method which comprises condensing a dihydroxyalkyl oxamide with a nitrazani-troalkylene diisocyanate.

9. As new' compositions of matter, -th e-nitro-substituted polyurethanepolymers prepared 'by'the method which comprises condensing a dialkoxynitrazaalkylene diol with a lower alkylene diisocyanate.

10. As new compositions of matter, the nitro-substituted polyurethane polymers prepared by the method which comprises condensing a dialkoxynitrazaalkylene diol with a nitroalkylene diisocyanate.

11. As new compositions of matter, the nitro-substituted polyurethane polymers prepared by the method which comprises condensing a dialkoxynitrazaalkylene diol with a nitrazaalkylene diisocyanate.

12. As new compositions of matter, the nitro-substituted polyurethane polymers prepared by the method which comprises condensing a dialkoxynitrazaalkylene diol with a 'nitrazanitro'alkylene diisocyanate.

13. The method of'pre'paring' polyurethane polymers which comprises condensing a diisocyanate composition selected from the group consisting of lower alkylene diisocyanates, nitroalkylene diisocyanates, nitrazaalkylene diisocyanates, -nitra'zani-troalkylene diisocyanates, and mixtures thereof with a diol composition selected from the group consisting of dialkoxynitrazaalkylene diols, dihydroxyalkyl oxamides, and mixtures thereof.

14. The method of claim 13 wherein said condensawherein x is a small whole number from to 6 inclusive, tion is carried out in the presence of a plasticizing agent. y is a small whole number from 1 to 3 inclusive, and X 15. The method of claim 13 wherein said condensation is a Whole number greater than one. is etfected in the presence of a condensation catalyst. 20. As new compositions of matter, the nitro poly- 16. The method of preparing nitro-substituted polyurethanes containing the structural unit:

r0 NO: 0 NO! urethane polymers which comprises condensing a diisowherein X is a whole number greater than one. cyanate composition selected from the group consisting 15 21. As new compositions of matter, the nitro polyof lower alkylene diisocyanates, nitroalkylene diisourethanes containing the structural unit:

L to. L l

cyanates, nitrazaalkylene diisocyanates, nitrazanitroalkylwherein X is a whole number greater than one. ene diisocyanates, and mixtures thereof with a diol com- 22. The method of preparing nitro polyurethanes conposition selected from the group consisting of dialkoxytaining the structural unit:

L L110, 1, to. L |x l.

which comprises condensing an alcohol having the genmtrazaalkylene drols, dlhydroxyalkyl oxamides, and mixeral formula:

tures thereof and a crosslinking agent. NO No 17. As new compositions of matter, the nitro poly- I i urethanes containing the structural unit "E J L Lto, J, to. L .L .L

wherein A, A, A" and A" are lower alkylene radicals, with a diisocyanate having the general formula: x is a small whole number from 0 to 6 inclusive, y is a small whole number from 0 to 2 inclusive, and X is a I -A"- H m whole number greater than one. 0 O N O o O 18. As new compositions of matter, the nitro poly- NOI Y urethanes containing the structural unit: wherein A, A, A, and A' are lower alkylene radicals,

L to. .L to. L 1 ix x is a small whole number from 0 to 6 inclusive, y is a wherein A is a lower alkylene radical, x 1s a small whole small whole number from 0 to 2 inclusive, and X is a number from 0 to 6 inclusive, y is a small whole number whole number greater than one from 0 to 2 inclusive, and X is a whole number greater 23. The method of claim 22 wherein the condensation than one.

reactlon 1s conducted in the presence of a catalyst selected As new 'Fq i g i i j the nitro polyfrom the group consisting of boron trifluoride, boron met anes contammg e S um um trifluoride complexes, and metal chelates.

L to, l. L .L .L

3,087,961 9 1,0 t 24. The-method of claim 22-wherein ;.the reaction is 301-Themethdtof preparingnit'ro polyurethanes conconducted in the presenceofboron trifluorjide. .taining-fthe sstructu'ral unit? Ne 3 F" 1. OYNH OHzCH:'-( J-CH:QHENH JJO GHiQHEO -QH2-:NQHq+O QHiOHEOE L l lo: |3L .|x wherein X is a whole number greater than one, which 25. The method of claim 22 wherein the reaction is QQfifPriSes 3,3-ffinitmpemanrlt-s-diisqcyanate conducted in the presence of boron trifluoride etherate.

26. The method ofeclaim 22 wherein the reaction is conducted in-the presence of iferric acetylacetonate. S w q i f the pQlyurethanes 27. The method-of preparing =nitro polyurethanes confl the stmcmr'ahumt" taining the structural unit-z u i i i: p p l -E0-NH -NH '-0-'- A! o-- z -o1l'o:|;

a whole number greater than one. p 32. As newcompositions of matter; the nitro poly- T 1, MGHPWATOH 2'5 urethanes camainmg 11116 structural units LILTOI L 1 102 JX wherein A, A, and A are lower alkylene radicals, x is a small whole number from O to 2 inclusive, and X is a whole number greater than one.

33. As new compositions of matter, the nitro polyurethanes containing the structural unit:

with a diisocyanate having the general formula:

Lilo J.

0 NO: 0 0 0 wherein A is a lower alkylene radical, x is a small whole 35 F]! I I H 1 number from 0 to 6 inclusive, y is a small whole number E "NH JJ O A NH CE NH ATO from 1 to 3 inclusive, and X is a whole number greater x than one.

wherein A and A are lower alkylene radicals and X is a whole number greater than one.

34. As new compositions of matter, the nitro polyl-o NO: I NO: NO; |:(%-NHCHaOH2-( JOHnCHz-NHCO-GHaGHzOOHaINOH N-CHgO OH1OH1O- Lie. 1. J. i.

which comprises condensing an alcohol having the genurethanes containing the structural unit:

wherein X is a whole number greater than one.

P1 Y 35. The method of preparing nitro polyurethanes con- H0CH2OH2O 3 E j -Jx taining the structural unit:

28. The method of preparing nitro polyurethanes containing the structural unit: 40

eral formula:

which comprises condensing an alcohol having the general formula:

with a diisocyanate having the general formula:

wherein x is a small whole number from 0 to 6 inclusive, With a dii cyanate having the general formula: y is a small whole number from 1 to 3 inclusive, and X is a whole number greater than one. F

29. The method of preparing nitro polyurethanes containing the structural unit:

N0, 0 NO: "I

to. L J. 1.

wherein X is a whole number greater than one, which comprises condensing 3,3-dinitropentane 1,5 diisocyanate with 5,7,9,1l-tetranitro-5,7,9,l1-tetra-aza-3,l3-oxy- 1,15-pentadecanediol.

wherein A, A, and A" are lower alkylene radicals, x is a small whole number from 0 to 2 inclusive, and X is a whole number greater than one.

36. The method of claim 35 wherein the condensation conducted in the presence of boron trifluoride.

wherein A and A are lower alkylene radicals and X is a whole number greater than one.

41. The method of preparing nitro polyurethanes containing the structural unit:

11 reaction is conducted in the presence of a catalyst selected from the group consisting of boron trifluoride, boron trifluoride complexes, and metal chelates.

37. The method of claim 35 wherein the reaction is wherein X is a whole number greater than one, which comprises condensing 3,3-dinitro-l,5-pentane diisocyamate and N,N-bis(2hydroxyethyl) oxamide.

42. As new compositions of matter, the nitropolyurethanes containing the structural unit:

wherein Y is a lower nitroalkylene radical, A is a lower alkylene radical, and X is a whole number greater than one.

which comprises condensing an alcohol having the general formula:

0 0 HO-ANH NH-AOH with a diisocyanate having the general formula:

25 No references cited. 

1. AS NEW COMPOSITIONS OF MATTER, THE NITRO-SUBSTITUTED, POLYURETHANE POLYMERS PREPARED BY THE METHOD WHICH COMPRISES CONDENSING A DISOCYNATE COMPOSITION SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYLENE DIISOCYANATES, NITROALKYLENE DISOCYANATES, NITRAZAALYLENE DIISOCYANATES, NIRAZANITROALKYLENE DIIOCYANATES, AND MIXTURES THEREOF WITH A DIOL COMPOSITION SELCTED FROM THE GROUP CONSISTING OF DIALKOXYNITRAZAALKYLENE DIOLS, DIHYDROXYALKYL OXAMIDES, AND MIIXTURES THEREOF. 